Method of making a connector

ABSTRACT

A method of making a connector comprising bending a tube to form a bend portion and forcing a plurality of balls through the passage in the tube to appropriately shape the cross section of the passage. An insulator and inner conductor are forced into the bent tube with the tube forming a die for shaping of the insulator and inner conductor.

United States Patent Dunbabin 1 51 May 30, 1972 54 METHOD OF MAKING ACONNECTOR 2,869,377 1 1959 Pieterse ..74/216.3 2,945,203 7/ 1960Quackenbush. .....339/59 I Z [72] G El Cahf 3,183,472 5/1965 Pawl..29/629 [73] Assignee: Connecting Devices, Inc., El Segundo, 3,335,4858/1967 Russo ..29/455 Califi 3,457,540 7/1969 Rolfes ..339/89 [22]Filed: July 22 1969 1,095,265 5/1914 Brinkman ..72/370 2,914,839 12/1959Schwenger ..29/148.4 [21] Appl. No.: 843,459

Primary Examiner-John F. Campbell 52 US. Cl ..29/629 339/59 339 97455mm" 74 2 3 i9/ 4 4: 72/376 Attorney-Smyth, ROSIOII & Pavitt [51] Int.Cl. ..H02g 15/00 [58] Field of Search ..29/629, 626, 630 R, 630 A,ABSTRACT 29/630 148A; 339/97 59; 74/2163; A method of making a connectorcomprising bending a tube 72/370 to form a bend portion and forcing aplurality of balls through the passage in the tube to appropriatelyshape the cross sec- [56] References Cmd tion of the passage. Aninsulator and inner conductor are UNITED STATES PATENTS forced into thebent tube with the tube forming a die for shaping of the insulator andinner conductor. 2,747,059 5/1956 Cockerham ..29/630 2,856,674 10/1956Hill .339/89 15 Claims, 7 Drawing Figures METHOD OF MAKING A CONNECTORBACKGROUND OF THE INVENTION The present invention relates to a method ofmaking an angle connector of the type including a tubular outerconductor, a central or inner conductor within the outer conductor andan insulator for mounting the inner conductor within the outer conductorand for spacing the two conductors. Suitable connector elements areprovided at opposite ends of the connector to provide for electricallyand mechanically joining the opposite ends of the connector toconductive elements such as coaxial cable. The connector is bent througha predetermined angle such as 90 so that the conductive elementsconnected thereby can be joined at the desired angle.

In making connectors of this type it is important that the passagethrough the tube or outer conductor have a perfectly circular crosssectional configuration. This is necessary to assure that the connectorwill have the desired electrical qualities such as good impedancematching characteristics. If the outer conductor is simply bent to thedesired angle, the internal diameter of the bend portion takes on agenerally elliptical configuration which is very undesirableelectrically in that it produces poor impedance matching.

In an effort to solve these problems, it has been proposed to constructthe tube in half sections and then join the half sections in a brazingoperation. This process is difiicult because the mating faces of thehalf sections must be finished prior to brazing and because it isdifficult to accurately align the half sections for the brazingoperation so that no discontinuities of the type which would impair theelectrical characteristics of the outer conductor would be formed. Dueto the nature of the brazing and alignment operations it is virtuallyimpossible to make a perfectly circular passage through the-ultimatelyformed tube.

Also, even if the brazing operation is carefully carried out, smallpinholes may be formed in the ultimately formed outer conductor. Thesepinholes cause discontinuities which have an adverse effect on theelectrical characteristics of the connector. Specifically, the pinholesmay cause a frequency shift and/or a voltage drop. Furthermore, moisturemay enter the pinholes and provide a conductive path between the innerconductor and the outer conductor.

SUMMARY OF THE INVENTION The present invention solves these problems byproviding integral outer conductor with a bend portion having a passagetherethrough which is of circular cross section. Brazing of halfsections and the consequent disadvantages thereof are eliminated.

According to the present invention, the tube for the outer conductor isfirst bent to the desired angle. This inherently causes the tube todistort with the result that the passage at the bend portion assumes anoncircular configuration such as a generally elliptical configuration.To make the passage of circular cross section at the bend portion, thepresent invention provides for the forcing of one or more balls throughthe passage. The ball should have a larger diameter than the minor axisof the elliptical passage so that the ball can deform the material ofthe tube and reshape the passage to the desired circular configuration.

In a preferred form of the invention, the passage is progressivelyshaped through the use of a plurality of balls each having a largerdiameter than the previously used ball. In this fashion, the ellipticalpassage at the bend portion is progressively converted into a circularpassage of the desired diameter.

In addition to accurately shaping the passage, the movement of the ballsthrough the passage burnishes the wall of the passage. This furtherimproves the electrical characteristics of the outer conductor.

Although this feature of passage shaping is particularly adapted forconverting a noncircular passage into a passage having a circular crosssection, it may be applied to make the passage of other cross sectionalconfigurations. Similarly, this principle of the invention may beapplied to shaping of the intemal surface of a tube which is ultimatelyused for purposes other than an outer conductor for an angle connectorsuch as wave guides.

It is preferred to fill the tube with a bendable filler material priorto bending of the tube. This tends to reduce, but does not eliminate,the extent to which the passage becomes noncircular as a result of thebending operation. Following the bending of the tube, the bendablematerial therein can be removed as by melting of the filler material.

After the outer conductor has been formed, the insulator and innerconductor are inserted as a unit into the passage of the outerconductor. The outer conductor serves as a die for shaping of theinsulator and inner conductor as the latter are forced into the passage.A region of the inner conductor is preferably annealed to facilitate thebending thereof. The resultant structure has excellent electricalproperties.

The invention, both as to its organization and method of operationtogether with further features and advantages thereof may best beunderstood by reference to the following description taken in connectionwith the accompanying illustrative drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a sectional view taken on anaxial plane of an illustrative connector which has been constructed inaccordance with the method of this invention.

FIG. 2 is a side elevational view of a tube which is to be formed intothe outer conductor of the connector.

FIG. 3 is an elevational view showing the tube after it has been bent.

FIG. 4 is a sectional view taken along line 4-4 of FIG. 3 andillustrating the general configuration of the bend portion of the tubefollowing the bending thereof.

FIG. 5 is a sectional view on an axial plane through the bent tubeillustrating the process of forcing a series of balls through the tubeto appropriately shape the passage at the bend portion of the tube.

FIG. 6 is a sectional view taken along line 6--6 of FIG. 5 illustratinga typical general configuration of the tube after it has been subjectedto the action illustrated in FIG. 5.

FIG. 7 is a sectional view on an axial plane illustrating the insertionof the insulator and inner conductor into the outer conductor.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing and inparticular to FIG. 1 thereof, reference numeral 11 designates anelectrical connector constructed in accordance with the method of thisinvention. The connector 11 generally comprises an outer conductor 13,an inner conductor 15 and an insulator 17 separating the conductors. Inthe embodiment illustrated, the connector 1 1 has been bent through anangle of 90 although the particular angle which is formed by theconnector can be varied to suit external conditions.

The outer conductor 13 is constructed of a deformable conductive metal.Preferably the metal for the outer conductor 13 is nonmagnetic asmagnetic materials could adversely affect I the electricalcharacteristics of the connector. The outer conductor 13 may beconstructed, for example, of brass, aluminum, or stainless steel with304 stainless steel being preferred.

The outer conductor 13 has an axial passage 19 extending completelytherethrough. The passage is formed by a wall 21 of the tube 13. Thepassage 19 is of circular cross section throughout the full lengththereof so as to provide excellent electrical characteristics for theconnector 1 1.

The inner or central conductor 15, in the embodiment illustrated, is inthe form of an elongated rod which is coaxial with the passage 19 andwith the outer conductor 13. The inner conductor 15 is mounted withinthe outer conductor 13 by the insulator 17. The inner conductor has amale end 23 and a female end which is defined by a plurality of axiallyextending spring fingers which provide a socket 27. The female end ofthe connector 11 is adapted to receive the male end of an externalmember (not shown) such as the male end 23 and the male end 23 isadapted to be received within the female portion of an external member(not shown) such as the socket 27.

The inner conductor 15 is preferably constructed of a nonmagneticconductive metal having spring qualities such as beryllium copper. Thespring qualities are necessary for the spring fingers 25. The entireinner conductor 15 except for the spring fingers 25 may be annealed tofacilitate bending thereof.

The insulator 17 fits snugly within the passage 19 and is coaxialtherewith. The inner conductor 15 fits snugly within an axial passagewhich extends through the insulator 17. The female end of the innerconductor 15 is flush with one end of the insulator 17 and the male end23 projects outwardly beyond the other end of the insulator. Theinsulator may be of various materials having electrical insulatingqualities with polytetrafluoroethylene being preferred.

At the female end of the connector 1 1, the outer conductor 13 has beenmachined to form an end portion 29 of reduced wall thickness. A boss 31having external threads 33 telescopically receives the end portion 29and is rigidly affixed thereto as by brazing. The boss 31 forms, ineffect, an extension of the outer conductor 13 and houses a portion ofthe insulator l7.

Adjacent the male end of the connector 11, the outer conductor 13 hasbeen machined to form an annular groove 35 and an end portion 37 ofreduced wall thickness. A retaining ring 39 is received with groove 35and within an internal groove 41 of a nut 43 to rotatably mount thelatter on the outer conductor 13. The nut 43 has internal threads 45 forconnection to an external member (not shown). An annular seal 47 ismounted on the end portion 37 and provides a seal between such endportion and the internal surface of the nut 43.

The outer conductor 13 is formed from a cylindrical tube 49 (FIG. 2)having a cylindrical passage 51 extending therethrough. The tube 49 isfilled with a low melting point bendable material such as the materialsold the trademark Ceriban. The tube 49 is then bent through the desiredangle utilizing appropriate tooling for accomplishing this purpose toform the bend portion 53 (FIG. 3). The Ceriban is then heated to atemperature above its melting point but below the melting point of thematerial of the tube 49 to allow the former to flow out of the passage51.

The result of bending of the tube 49 is that the passage 51 assumes anelliptical configuration at the bend portion 53 as shown in FIG. 4. Thewall thickness of the tube 49 at the bend portion 53 will be differentat different circumferential locations. Generally, however, the wallthickness of the tube 49 will be greater along the inside 55 of the bendportion than along the outside 57 of the bend portion. The use of theCeriban within the tube 49 prior to bending of the tube reduces theamount to which the passage 55 becomes noncircular as a result of thebending operation.

Next, the tube 49 is placed in a suitable fixture 59 which may be ofconventional construction and for this reason is shown diagrammaticallyin FIG. 5. The fixture 59 retains the tube 49 while a first hardspherical ball 61 is positioned in the upper end of the passage 51. Theportion of the passage 51 which is not at the bend portion will remaincircular and will be unaffected by the bending operation. Accordingly,the ball 61 will fall through such circular portion of the passage untilfurther movement thereof is prevented by the elliptical portion of thepassage 51. The ball 61 is sized so as to have a diameter which islarger than the minor axis of the elliptical portion of the passage sothat it can exert a reshaping effect on such portion of the passage.Next, balls 63, 65, and 67 of progressively increasing diameters arepositioned in the passage 51 and driven therethrough utilizing a ramsuch as a hydraulically operated ram 69. Although any suitable number ofthe balls may be utilized, depending upon the results desired, it willusually be desirable to utilize three or four of the balls with each ofthe balls being of progressively increas ing diameter.

The balls must be sufficiently hard so that they can deform the tube 49sufficiently to form the passage 51 into a circular configuration asshown in FIG. 6. Because of the inherent springback of the material ofthe tube 49, the last of the forming balls utilized should be ofslightly larger diameter than the desired diameter of the passage 51 atthe bend portion 53. The last forming ball 67 is forced through thepassage 51 using one or more balls 68 of smaller diameter than the ball67 and the passage 51. Preferably, at the completion of the operationshown in FIG. 5, the diameter of the passage 51 will be constantthroughout the full length thereof. Although the bending of the tube 49and the forcing of the balls therethrough may affect the wall thicknessof the tube 49, this will not affect the electrical characteristics ofsuch tube when the latter is utilized as an outer conductor for aconnector.

The tube 49 is then removed from the fixture 59 and the reducedthickness end portions 29 and 37 and the groove 35 are formed as bymachining. Next the end faces of the tube 49 are made perfectly squarewith the axis of the passage. With the completion of these operations,the tube 49 is converted into the outer conductor 13.

The boss 31 is then pressed on the end portion 29 and brazed to theouter conductor 13 as shown in FIG. 1. The resultant construction isthen plated, first with nickle and then with gold, in order to give itbetter conductive properties.

Assuming that the center conductor 15 and the insulator 17 have beenpreformed, the center conductor 15 may be inserted within the axialpassage through the insulator 17 as shown in FIG. 7. When in thiscondition, the inner conductor 15 and the insulator 17 are both straightcylindrical members. Prior to the insertion of the inner conductor 15,the entire inner conductor 15 except for the spring fingers 25 should beannealed to facilitate bending thereof and the spring fingers 25 shouldbe heat treated to impart substantial resilience thereto. The outerconductor 13 and the boss 31 can be retained in a suitable fixture 71having a tubular extension 72 for slidably retaining the insulator 17.Utilizing an appropriate ram 73 the insulator l7 and the inner conductor15 can be forced into the passage 51 as shown in FIG. 7. As downwardmovement of the ram 73 progresses, the inner conductor 15 and theinsulator 17 are gradually subjected to the progressive curving of thepassage 51. This results in distortion of the inner conductor 15 and ofthe insulator 17. Thus, the outer conductor 13 serves as a die forforming of the inner conductor 15 and the insulator 17. The insulatorfits snugly within the outer conductor 13. Next, the insulator 17 at theend thereof adjacent the male end 23 is trimmed as necessary and theretaining ring 39 and the nut 43 are mounted on the outer conductor 13.

The method described herein can be applied to connectors of many designsand to many other devices and is not restricted to the making of theparticular connector 11 illustrated in FIG. 1. Although an exemplaryembodiment of the invention has been shown and described, many changes,modifications, and substitutions may be made by one having ordinaryskill in the art without necessarily departing from the spirit and scopeof this invention.

We claim:

1. A method of forming a tube having a curved portion with a passage ofa predetermined cross sectional configuration extending therethrough,said method comprising:

providing a tube having a curved portion and a curved passage extendingthrough said curved portion, said passage having a cross sectionalconfiguration other than said predetermined cross sectionalconfiguration, said tube being constructed of deformable material;

forcing at least one member of approximately said predetermined crosssectional configuration through said curved passage to deform said tubeto thereby form said passage providing an insulator and an innerconductor with the with said predetermined cross sectional configurationat said curved portion; and

said predetermined cross sectional configuration being circular and saidmember being a substantially spherical ball, said step of forcingincluding forcing a plurality of 5 said balls of progressivelyincreasing diameter through said curved passage with the last of saidballs being of substantially said predetermined cross sectionalconfiguration.

2. A method of making an electrical connector comprising:

providing a tube of conductive material having a bend portion and apassage extending through said bend portion with said passage being ofcircular cross sectional con figuration;

inner conductor extending through the insulator and sized to snugly fitwithin said passage, at least a portion of said inner conductor beingannealed to facilitate subsequent bending thereof;

retaining said tube;

forcing said insulator and inner conductor into said passage of saidtube with the tube deforming said insulator and inner conductor as theinsulator and inner conductor are forced through said bend portion ofthe tube; and

said first mentioned step of providing including providing a tube ofdeformable material having a substantially cylindrical passage extendinggenerally axially therethrough, bending said tube about an axisgenerally transverse to the axis of said passage to form the bendportion with the passage extending through said bend portion and withthe bending of said tube distorting the passage through said bendportion to a generally elliptical cross sectional configuration, andforcing a plurality of balls of progressively increasing diameterthrough the passage through said bend portion to deform the material ofthe tube at the bend portion to provide the passageway through the bendportion with a circular cross sectional configuration.

3. A method of forming a tube comprising:

providing a tube having a curved portion and a curved passage extendingthrough said curved portion, said curved passage having a noncircularcross sectional configuration said tube being constructed of deformablematerial; and

forcing at least one ball through said curved passage to deform saidtube to thereby form said curved passage with a circular cross sectionalconfiguration, said step of forcing being carried out subsequent to saidstep of providing.

4. A method of forming a tube having a bend portion with a passage ofcircular cross section extending through and along said bend portion,said method comprising:

providing a unitary tube of deformable material having a substantiallycylindrical passage extending generally axially therethrough;

bending said unitary tube about an axis generally transverse to the axisof said passage to form a bend portion with the passage extendingthrough said bend portion and with the bending of said tube distoringthe passage through said bend portion to a noncircular cross sectionalconfiguration;

retaining the unitary tube; and

following the step of bending forcing at least one ball through thepassage through the bend portion to deform the material of the unitarytube at the bend portion to provide the passage through the bend portionwith a circular cross sectional configuration.

5. A method as defined in claim 4 wherein said step of forcing includesforcing a plurality of balls of progressively increasing diameterthrough said passage at said bend portion.

6. A method as defined in claim 4 including filling the unbent tube witha deformable filler material and subsequently bending said tube aboutsaid axis, said method including the step of removing said deformablefiller material from said passage of said tube prior to said step offorcing.

7. A method of making an electrical connector comprising:

providing a tube of deformable conductive material having a bend portionand a curved passage of noncircular cross sectional configurationextending through said bend portion; retaining said tube; forcing atleast one ball through the passage through the bend portion to deformthe material of the tube at the bend portion to provide the passagethrough the bend portion with a circular cross sectional configuration;

inserting an inner conductor into said passage; and

providing an insulator within said passage with the insulator spacingthe inner conductor from the tube and with the insulator and innerconductor extending at least partially through the bend portion, saidstep of inserting being carried out subsequent to said step of forcing.

8. A method as defined in claim 7 wherein said step of forcing includesforcing a plurality of balls of progressively increasing diameterthrough said passage at said bend portion with the last of said ballsbeing slightly larger than the desired cross sectional configuration ofsaid passage at said bend portion to thereby allow for springback of thetube.

9. A method as defined in claim 7 wherein said step of insertingincludes providing an insulator of deformable material and an innerconductor of deformable material with the insulator and inner conductorbeing substantially straight and with the inner conductor extendingthrough said insulator, retaining said tube and forcing said insulatorand inner conductor into said passage of said tube with the tubedeforming said insulator and inner conductor to the desire configurationat said bend portion.

10. A method as defined in claim 2 wherein said step of providing aninsulator and inner conductor includes providing the inner conductorwith female connector means having resilient spring qualities, saidportion of said center conductor which is annealed being a portion otherthan said female connector means.

11. A method as defined in claim 4 including the step of providingelectrically conductive terminals adjacent the opposite end portions ofsaid tube.

12. A method as defined in claim 7 wherein the first mentioned step ofproviding includes providing an axially unsplit tube and bending saidtube to form said passage thereof into said noncircular cross sectionalconfiguration, said step of forcing being carried out subsequent to saidstep of bending.

13. A method as defined in claim 3 wherein said step of forcing includesforcing a plurality of balls of progressively increasing diameterthrough said curved passage.

14. A method of forming a tube comprising:

providing a unitary tube of deformable material having a passage ofpredetermined cross sectional configuration extending generally axiallytherethrough;

bending said unitary tube about an axis generally transverse to the axisof said passage to form a bend portion with the passage extendingthrough said bend portion and with the bending of said tube distortingthe passage through said bend portion to a cross sectional configurationother than said predetermined cross sectional configuration; retainingthe unitary tube; and

following the stp of bending forcing at least one member ofsubstantially said predetermined cross sectional configuration throughthe passage through the bend portion to deform the material of theunitary tube at the bend portion to provide the passage through the bendportion with substantially said predetermined cross sectionalconfiguration.

15. A method as defined in claim 14 wherein said one member is a firstmember and including a second member having a cross sectionalconfiguration geometrically similar to and smaller than said firstmember, said step of forcing includes forcing said second member throughthe passage through the bend portion to deform the material of the tubeat the bend portion prior to forcing said first member through thepassage through the bend portion.

1. A method of forming a tube having a curved portion with a passage ofa predetermined cross sectional configuration extending therethrough,said method comprising: providing a tube having a curved portion and acurved passage extending through said curved portion, said passagehaving a cross sectional configuration other than said predeterminedcross sectional configuration, said tube being constructed of deformablematerial; forcing at least one member of approximately saidpredetermined cross sectional configuration through said curved passageto deform said tube to thereby form said passage with said predeterminedcross sectional configuration at said curved portion; and saidpredetermined cross sectional configuration being circular and saidmember being a substantially spherical ball, said step of forcingincluding forcing a plurality of said balls of progressively increasingdiameter through said curved passage with the last of said balls beingof substantially said predetermined cross sectional configuration.
 2. Amethod of making an electrical connector comprising: providing a tube ofconductive material having a bend portion and a passage extendingthrough said bend portion with said passage being of circular crosssectional configuration; providing an insulator and an inner conductorwith the inner conductor extending through the insulator and sized tosnugly fit within said passage, at least a portion of said innerconductor being annealed to facilitate subsequent bending thereof;retaining said tube; forcing said insulator and inner conductor intosaid passage of said tube with the tube deforming said insulator andinner conductor as the insulator and inner conductor are forced throughsaid bend portion of the tube; and said first mentioned step ofproviding including providing a tube of deformable material having asubstantially cylindrical passage extending generally axiallytherethrough, bending said tube about an axis generally transverse tothe axis of said passage to form the bend portion with the passageextending through said bend portion and with the bending of said tubedistorting the passage through said bend portion to a generallyelliptical cross sectional configuration, and forcing a plurality ofballs of progressively increasing diameter through the passage throughsaid bend portion to deform the material of the tube at the bend portionto provide the passageway through the bend portion with a circular crosssectional configuration.
 3. A method of forming a tube comprising:providing a tube having a curved portion and a curved passage extendingthrough said curved portion, said curved passage having a noncircularcross sectional configuration said tube being constructed of deformablematerial; and forcing at least one ball through said curved passage todeform said tube to thereby form said curved passage with a circularcross sectional configuration, said step of forcing being carried outsubsequent to said step of providing.
 4. A method of forming a tubehaving a bend portion with a passage of circular cross section extendingthrough and along said bend portion, said method comprising: providing aunitary tube of deformable material having a substantially cylindricalpassage extending generally axially therethrough; bending said unitarytube about an axis generally transverse to the axis of said passage toform a bend portion with the passage extending through said bend portionand with the bending of said tube distoring the passage through saidbend portion to a noncircular cross sectional configuration; retainingthe unitary tube; and following the step of bending forcing at least oneball through the passage through the bend portion to deform the materialof the unitary tube at the bend portion to provide the passage throughthe bend portion with a circular cross sectional configuration.
 5. Amethod as defined in claim 4 wherein said step of forcing includesforcing a plurality of balls of progressively increasing diameterthrough said passage at said bend portion.
 6. A method as defined inclaim 4 including filling the unbent tube with a deformable fillermaterial and subsequently bending said tube about said axis, said methodincluding the step of removing said deformable filler material from saidpassage of said tube prior to said step of forcing.
 7. A method ofmaking an electrical connector comprising: providing a tube ofdeformable conductive material having a bend portion and a curvedpassage of noncircular cross sectional configuration extending throughsaid bend portion; retaining said tube; forcing at least one ballthrough the passage through the bend portion to deform the material ofthe tube at the bend portion to provide the passage through the bendportion with a circular cross sectional configuration; inserting aninner conductor into said passage; and providing an insulator withinsaid passage with the insulator spacing the inner conductor from thetube and with the insulator and inner conductor extending at leastpartially through the bend portion, said step of inserting being carriedout subsequent to said step of forcing.
 8. A method as defined in claim7 wherein said step of forcing includes forcing a plurality of balls ofprogressively increasing diameter through said passage at said bendportion with the last of said balls being slightly larger than thedesired cross sectional configuration of said passage at said bendportion to thereby allow for springback of the tube.
 9. A method asdefined in claim 7 wherein said step of inserting includes providing aninsulator of deformable material and an inner conductor of deformablematerial with the insulator and inner conductor being substantiallystraight and with the inner conductor extending through said insulator,retaining said tube and forcing said insulator and inner conductor intosaid passage of said tube with the tube deforming said insulator andinner conductor to the desire configuration at said bend portion.
 10. Amethod as defined in claim 2 wherein said step of providing an insulatorand inner conductor includes providing the inner conductor with femaleconnector means having resilient spring qualities, said portion of saidcenter conductor which is annealed being a portion other than saidfemale connector means.
 11. A method as defined in claim 4 including thestep of providing electrically conductive terminals adjacent theopposite end portions of said tube.
 12. A method as defined in claim 7wherein the first mentioned step of providing includes providing anaxially unsplit tube and bending said tube to form said passage thereofinto said noncircular cross sectional configuration, said step offorcing being carried out subsequent to said step of bending.
 13. Amethod as defined in claim 3 wherein said step of forcing includesforcing a plurality of balls of progressively increasing diameterthrough said curved passage.
 14. A method of forming a tube comprising:providing a unitary tube of deformable material having a passage ofpredetermined cross sectional configuration extending genErally axiallytherethrough; bending said unitary tube about an axis generallytransverse to the axis of said passage to form a bend portion with thepassage extending through said bend portion and with the bending of saidtube distorting the passage through said bend portion to a crosssectional configuration other than said predetermined cross sectionalconfiguration; retaining the unitary tube; and following the stp ofbending forcing at least one member of substantially said predeterminedcross sectional configuration through the passage through the bendportion to deform the material of the unitary tube at the bend portionto provide the passage through the bend portion with substantially saidpredetermined cross sectional configuration.
 15. A method as defined inclaim 14 wherein said one member is a first member and including asecond member having a cross sectional configuration geometricallysimilar to and smaller than said first member, said step of forcingincludes forcing said second member through the passage through the bendportion to deform the material of the tube at the bend portion prior toforcing said first member through the passage through the bend portion.